This invention relates to a method of peening surfaces and more particularly to a method of peening relatively movable surfaces in an internal combustion engine to reduce the fuel and lubricant consumption of the engine.
The present invention, while of general application, is particularly well suited for use in the peening of the cylinder sleeves or walls in an internal combustion engine of the reciprocating type. As is well known, such engines include one or more pistons which customarily are provided with rings in sliding contact with the inner cylindrical walls of the sleeves or cylinders of the engine. The frictional resistance to this sliding contact is a function, inter alia, of the amount and quantity of lubricant between the cylinder walls and the piston rings, the hardness of the wall surfaces, and the smoothness of the walls, both initially and after being subjected to wear following the operation of the engine over an extended period. As the frictional resistance between these relatively movable surfaces decreases, the amount of energy needed to operate the engine also decreases with a corresponding reducton in the engine's fuel consumption.
Heretofore, attempts to reduce the frictional resistance between relatively movable surfaces in an internal combustion engine have exhibited a number of disadvantages. As an illustration, in many engines of this type it is advantageous to maintain a thin film of oil or other liquid lubricant between the two surfaces. If the surfaces are excessively smooth, the lubricant does not readily stay in place, and yet as the roughness of the surface increases there is a corresponding increase in friction. Primarily because of the close tolerances required between such components as the piston rings and the cylinder walls, prior peening techniques have not been entirely satisfactory in resolving the problem of providing sufficiently smooth surfaces while at the same time retaining a sufficient degree of roughness for good lubricant retention. In addition, in many cases the depressions resulting from the peening particles have been too large and deep to be of real practical value, while in other instances the particles left a multiplicity of irregularly shaped indentations which again were unsatisfactory in providing a meaningful reduction in frictional resistance and hence fuel consumption.